Ferrite materials are the common method for electronic phase shifter implementation. Ferrites are anisotropic, i.e., the phase shift of the energy in one direction is not replicated in the reverse direction. Ferrite phase shift is accomplished by applying a large current pulse, typically several amps in value, to the ferrite to establish a change in the large magnetic field and thereby adjusting the phase propagation characteristic of the material. Due to the hysteresis phenomena of ferrites, in order to change the phase another large current pulse is required to reset the phase to a stable reference phase state, followed by a second large pulse to establish the final phase state. The large current pulse requirements, as well as, the multiple pulses make the bias circuitry complex, costly and limited in speed. The phase shifters are also lossy. As the operating frequency increases, the size and coupling of such phase shifters to associated circuits is a major issue.
Another common method is to employ FET or PIN diode MMIC switches that switch in additional microstrip line lengths to realize a phase shifter. This additive line length provides the additional phase shift. Again, rather complex, external bias drive circuits are required to implement the switch bias. The PIN diode based systems require large levels of bias current, which further complicates the architecture. The individual switches are also lossy.
A more recent method is to employ voltage variable, dielectric material, like barium strontium titanate (BST). This material however, when employed in a phase shifter configuration requires ten thousand (10 Kv) volts of bias and is an extremely lossy medium for the propagation of RF energy.